﻿using System;
using System.Web;
using System.Drawing;
using System.Drawing.Imaging;
using System.IO;
using System.Configuration;
using System.Text.RegularExpressions;

namespace eWebapp
{
    ///   
    /// 防盗链IHttpHandler  
    /// 参考http://www.softat.org/archiver/tid-52114.html  
    /// 垃圾猪 2005-9-12 修正  
    ///   
    public class NoLink : IHttpHandler
    {
        private string eWebapp_NoLink = string.Empty;
        private string eWebapp_AllowLink = string.Empty;
        private bool eWebapp_AllowOnlyFile = true;

        private string eWebapp_NoLink_Message = string.Empty;
        private bool error = false;

        public NoLink()
        {
            //  
            // TODO: 在此处添加构造函数逻辑  
            //  
        }

        public void ProcessRequest(HttpContext context)
        {
            eWebapp_NoLink_Message = ConfigurationSettings.AppSettings["eWebapp_NoLink_Message"];
            string myDomain = string.Empty;
            error = errorLink(context, out myDomain);
            if (Empty(eWebapp_NoLink_Message))
            {
                eWebapp_NoLink_Message = "Link from :" + myDomain;
            }

            if (error)
            {
                //Jpg(context.Response,eWebapp_NoLink_Message);  
                Jpg(context.Response, eWebapp_NoLink_Message);
            }
            else
            {
                Real(context.Response, context.Request);
            }
        }

        public bool IsReusable
        {
            get
            {
                return true;
            }
        }

        ///   
        /// 输出错误信息  
        ///   
        ///   
        ///   
        private void Jpg(HttpResponse Response, string _word)
        {

            int myErrorWidth = _word.Length * 15;
            int myErrorHeight = 16;
            try
            {
                int _myErrorWidth = Convert.ToInt32(ConfigurationSettings.AppSettings["eWebapp_Error_Width"]);
                if (_myErrorWidth > 0)
                {
                    myErrorWidth = _myErrorWidth;
                }

            }
            catch
            {

            }
            try
            {
                int _myErrorHeight = Convert.ToInt32(ConfigurationSettings.AppSettings["eWebapp_Error_Height"]);
                if (_myErrorHeight > 0)
                {
                    myErrorHeight = _myErrorHeight;
                }
            }
            catch
            {

            }
            Bitmap Img = null;
            Graphics g = null;
            MemoryStream ms = null;
            Img = new Bitmap(myErrorWidth, myErrorHeight);
            g = Graphics.FromImage(Img);
            g.Clear(Color.White);
            Font f = new Font("Arial", 9);
            SolidBrush s = new SolidBrush(Color.Red);
            g.DrawString(_word, f, s, 3, 3);
            ms = new MemoryStream();
            Img.Save(ms, ImageFormat.Jpeg);
            Response.ClearContent();
            Response.ContentType = "image/Gif";
            Response.BinaryWrite(ms.ToArray());
            g.Dispose();
            Img.Dispose();
            Response.End();
        }

        ///   
        /// 输出真实文件  
        ///   
        ///   
        ///   
        private void Real(HttpResponse response, HttpRequest request)
        {
            FileInfo file = new System.IO.FileInfo(request.PhysicalPath);
            response.Clear();
            response.AddHeader("Content-Disposition", "filename=" + file.Name);
            response.AddHeader("Content-Length", file.Length.ToString());
            string fileExtension = file.Extension.ToLower();

            //这里选择输出的文件格式  
            //可以参考http://ewebapp.cnblogs.com/articles/234756.html增加对更多文件格式的支持.  

            switch (fileExtension)
            {

                case "mp3":
                    response.ContentType = "audio/mpeg3";
                    break;

                case "mpeg":
                    response.ContentType = "video/mpeg";
                    break;

                case "jpg":
                    response.ContentType = "image/jpeg";
                    break;

                case "bmp":
                    response.ContentType = "image/bmp";
                    break;

                case "gif":
                    response.ContentType = "image/gif";
                    break;

                case "doc":
                    response.ContentType = "application/msword";

                    break;
                case "css":
                    response.ContentType = "text/css";
                    break;

                default:
                    response.ContentType = "application/octet-stream";
                    break;

            }
            response.WriteFile(file.FullName);
            response.End();
        }

        ///   
        /// 确认字符串是否为空  
        ///   
        ///   
        ///   
        private bool Empty(string _value)
        {
            if (_value == null | _value == string.Empty | _value == "")
            {
                return true;
            }
            else
            {
                return false;
            }
        }

        ///   
        /// 检查是否是非法链接  
        ///   
        ///   
        ///   
        ///   
        private bool errorLink(HttpContext context, out string _myDomain)
        {
            HttpResponse response = context.Response;
            string myDomain = context.Request.ServerVariables["SERVER_NAME"];
            _myDomain = myDomain;
            string myDomainIp = context.Request.UserHostAddress;

            eWebapp_NoLink = ConfigurationSettings.AppSettings["eWebapp_NoLink"];
            eWebapp_AllowLink = ConfigurationSettings.AppSettings["eWebapp_AllowLink"];

            try
            {
                eWebapp_AllowOnlyFile = Convert.ToBoolean(ConfigurationSettings.AppSettings["eWebapp_AllowOnlyFile"]);
            }
            catch
            {
                eWebapp_AllowOnlyFile = true;
            }

            if (context.Request.UrlReferrer != null)
            {

                //判定referDomain是否存在网站的IP或域名  
                string referDomain = context.Request.UrlReferrer.AbsoluteUri.Replace(context.Request.UrlReferrer.AbsolutePath, "");
                string myPath = context.Request.RawUrl;

                if (referDomain.IndexOf(myDomainIp) >= 0 | referDomain.IndexOf(myDomain) >= 0)
                {
                    return false;
                }
                else
                {
                    //这里使用正则表达对规则进行匹配  
                    try
                    {
                        Regex myRegex;

                        //检查允许匹配  
                        if (!Empty(eWebapp_AllowLink))
                        {

                            myRegex = new Regex(eWebapp_AllowLink);

                            if (myRegex.IsMatch(myPath))
                            {
                                return false;
                            }

                        }

                        //检查禁止匹配  
                        if (!Empty(eWebapp_NoLink))
                        {

                            myRegex = new Regex(eWebapp_NoLink);
                            if (myRegex.IsMatch(myPath))
                            {
                                return true;
                            }
                            else
                            {
                                return false;
                            }
                        }
                        return true;
                    }
                    catch
                    {
                        //如果匹配出错，链接错误  
                        return true;
                    }
                }
            }
            else
            {
                //是否允许直接访问文件  
                if (eWebapp_AllowOnlyFile)
                {
                    return false;
                }
                else
                {
                    return true;
                }
            }
        }
    }
}

